He first appeared alongside Claudia Kuroi. Rhadamanthus later went to observe Rindo Urushiba and Smith, he was about to do something to them, but he cancelled his intention. He later appeared meeting alongside the other ARES members. When the ESP Police captured both Minami Azuma and Kozuki Kuroi, Rhadamanthus appeared and controlled a mass of crowd to corner the police and get them. However, he eventually failed. When the other Are members managed to capture Kozuki Kuroi, that knew the location of the Ark. Rhadamanthus used his power to command Kozuki to bring the Ark. While Kozuki did as he told. She used her remote teleportation to summon the Ark, thus Ares managed to obtain the Ark.

Rhadamanthus was killed by the Professor.

Later, Rinka Urushiba and her comrades invaded Ares' hideout. causing Ares' members to be interrupted in the middle of awakening the Messiah's power. He was later engaged in a fight against them, and was mortally wounded by Minami Azuma, who stabbed him in the shoulder. Due to chaos that done by Claudia, the intruders separated themselves. However, he was able to find Minami and Nadja Koroshinskii. He controlled the people there to corner both Minami and Nadja. He killed Minami by beheading her head, but later revealed that it was just illusions. Shortly the Professor appeared. He stated that he has been looking for an esper who has the same ability as Rhadamanthus, and asked him whether he was the one who killed the Diplomat. While Rhadamanthus kept silent, the Professor commented that he didn't need to answer anymore. The Professor killed Rhadamanthus, brutally cutting him into pieces.

Mind Control: His power is mind control. By producing a sound wave, those who hear it will be brainwashed and follow his command. His effective range is very wide. He can command a mass of people. Claudia Kuroi commented that he can control them just by being nearby, and that he never leaves evidence.